Cyano-13-epicobalamin (neovitamin B12) and its relatives

Abstract

An equilibration between cobinamide and neocobinamide with K≈ 1 occurs under highly acidic conditions. Similar equilibrations are reported with cobyric acid, other monocarboxylic acids, a dicarboxylic acid fraction, dehydrocobinamide, and with vitamin B12 itself. The last process gives neovitamin B12, which has been crystallised. Compounds of the neo-series resemble rather closely the analogous normal compounds, except in chiroptical properties.Methanolysis of vitamin B12 and of neocobinamide gives heptamethyl dicyanocobyrinate and heptamethyl dicyanoneocobyrinate, respectively, the mass spectra of which suggest that they are isomeric. This is confirmed by the X-ray analysis of neovitamin B12 which shows it to be cyano-13-epicobalamin. In relation to the naturally derived corrinoids known so far, the neo-compounds are thus epimeric at C-13.